Radially polarized optical parametric amplifier insensitive to polarization and amplification method thereof

Abstract

A radially polarized optical parametric amplifier insensitive to polarization is provided by the present invention, which comprises a laser module and a nonlinear crystal satisfying the type-II phase matching or the type-II quasi-phase matching condition, wherein the laser module is configured to generate two laser beams, namely the pump light and the signal light with an arbitrary polarization state, the wavelengths of the pump light and the signal light are degenerate or nearly degenerate; and the nonlinear crystal is provided in the emergent beamline of the laser module to perform optical parametric amplification of the signal light by using the pump light.

What is claimed is: 
     
         1 . A radially polarized optical parametric amplifier insensitive to polarization comprising a laser module and a nonlinear crystal satisfying a type-II phase matching or a type-II quasi-phase matching condition, wherein the laser module is configured to generate two laser beams, and the two laser beams are pump light and signal light, the signal light is of arbitrary polarization, wavelengths of the pump light and the signal light are degenerate or nearly degenerate, and the nonlinear crystal is provided in an emergent beamline of the laser module to perform optical parametric amplification of the signal light by using the pump light. 
     
     
         2 . The radially polarized optical parametric amplifier of  claim 1 , wherein different nonlinear crystals are used corresponding to the signal light with different wavelengths, so that gain of an o-polarized component and an e-polarized component of the signal light are equivalent and the signal light passing through the nonlinear crystal is capable of maintaining the original polarization state. 
     
     
         3 . The radially polarized optical parametric amplifier of  claim 1 , wherein the laser module comprises a first laser and a second laser, the first laser emits the pump light and the second laser emits the signal light;
 optionally, the laser module comprises a third laser, a beam splitter and a frequency converter, the laser emitted by the third laser passes through the beam splitter and two laser beams are obtained, one of which is the pump light and the other passes through the frequency converter and generates the signal light.   
     
     
         4 . The radially polarized optical parametric amplifier of  claim 3 , wherein the third laser is a Ti:sapphire femtosecond laser, which emits femtosecond pulsed laser, and the femtosecond pulsed laser passes through the beam splitter and two laser beams are obtained, one of which is the pump light and the other passes through the frequency converter and generates the signal light. 
     
     
         5 . The radially polarized optical parametric amplifier of  claim 3 , wherein the laser module further comprises a laser mode converter provided in the beamline of the signal light for changing the polarization state of the signal light. 
     
     
         6 . The radially polarized optical parametric amplifier of  claim 5 , wherein the laser mode converter is a vortex retarder for converting the linearly polarized signal light into the radially polarized signal light. 
     
     
         7 . The radially polarized optical parametric amplifier of  claim 3 , wherein the laser module further comprises a lens and a delay optical path, wherein the delay optical path is provided in the beamline of the signal light or the pump light, so that the signal light and the pump light are synchronized in time, the lens is provided in the beamline of the signal light or the pump light in such a way that the spot of the signal light is smaller than or equal to the spot of the pump light. 
     
     
         8 . The radially polarized optical parametric amplifier of  claim 1 , wherein when the nonlinear crystal performs optical parametric amplification of the signal light by using the pump light, another laser beam will be generated, which is idler light, in the nonlinear crystal, a non-collinear phase matching method is used, wherein the transmission directions of the signal light and the pump light are non-collinear, so as to separate the signal light passing through the nonlinear crystal from the pump light and the idler light;
 optionally, in the nonlinear crystal, a collinear phase matching method is used, wherein the transmission directions of the signal light and the pump light are collinear, and the optical parametric amplifier further comprises a beam splitter which is provided in the emergent beamline of the nonlinear crystal to separate the signal light passing through the nonlinear crystal from the pump light and the idler light.   
     
     
         9 . The radially polarized optical parametric amplifier of  claim 8 , wherein the beam splitter is a dichroic mirror which is highly transparent to the signal light and highly reflective to the pump light and the idler light;
 optionally, the beam splitter is a dichroic mirror which is highly transparent to the pump light and the idler light and highly reflective to the signal light.   
     
     
         10 . An optical parametric amplification method insensitive to polarization, wherein the method is applied to the radially polarized optical parametric amplifier of  claim 1 , the method comprises:
 using the laser module to generate two laser beams, wherein the two laser beams are pump light and signal light, wherein the signal light is of arbitrary polarization, and wavelengths of the pump light and the signal light are degenerate or nearly degenerate;   directing the pump light and the signal light through a nonlinear crystal, and performing optical parametric amplification of the signal light by using the pump light, wherein the nonlinear crystal is a nonlinear crystal satisfying the type-II phase matching or the type-II quasi-phase matching condition.